Over the short term, I’d put my money on the anti-liberals. Liberalism suffers from a series of weaknesses. First, many Americans have already betrayed it. The adventure of liberalism is constantly encountering people and ideas that are new and different. But Americans of both left and right moved into lifestyle enclaves with people like themselves. Americans have stopped seeing each other accurately. Conversation, the very lifeblood of liberalism, is blocked.

Second, liberal institutions have deteriorated. A liberal society needs universities where ideas are openly debated, it needs media outlets that strive to be objective, it needs political institutions, like the Senate, that are governed by procedures designed to keep the process fair to both sides. It needs people who put the rules of fair play above short-term partisan passion. Those people scarcely exist.

Third, Donald Trump. Trump marshaled illiberal groups in the G.O.P. and easily defeated the old guard. He turned the G.O.P. into an illiberal force. It’s very hard for Democrats to play by the rules of liberalism when the other party won’t.